Comparative Va

Topics: Chordate, Vertebra, Vertebrate Pages: 11 (2605 words) Published: June 25, 2013
-study of the structure(descriptive morphology) and of the functional significance of structure(fumctional morphology) of the vertebrate

Ontogenesis- development of the invidual
Phylogenesis-ancestral history; is is a study of history and of animals that no longer inhabit the earh and known to us by a fossil record *Craniates- hagfish and vertebrates

It is falling into two categories:
a. lacks vertebral columns (invertebrates)
b.with vertebral columns(vertebrates)

Protochordates- a dichotomy which is composed of marine animals which is not midway invertebrates and vertebrates -they do not have vertebral column but they share vertebrate characteristics, the four morphological features

Four Morphological Features:
a. notochord
b. dorsal hollow CNS
c. postanal tail
d. endostyle- glandular groove in the floor of the pharynx
*these features are the first ones who appears in an embryo
*without these features, an embryo cannot proceed to development but the postanal tail is less critical to development TAXONOMIC RELATION OF THE PROTOCHORDATES AND VERTEBRATES:
Kingdom Animalia
Phylum Chordata
Subphylum Urochordata
Subphylum Cephalochordata
Subphylum Craniata
Hagfish(w/o vertebrates)
Vertebrates(with vertebrates)

Chordates- animals with notochord at their embryo stage at least Craniates- chordates with a neurocranium(braincase)
Vertebrates- chordates with vertebrae
*Vertebrae appear during embryonic development after the notochord has formed. They may reinforce the notochord or replace it functionally.

-general pattern of primitive(plesiomorphic) and unique(derived) anatomical features. -exhibit similar but not identical patterns of embryonic development as a result of common ancestry -altering the morphology and developmental processes provides increasing opportunities for genetic changes that result in anatomic diversity


* The typical craniates body is made up of head, trunk and post anal tail A. HEAD
* Within the head are special sense organs for monitoring the external environment:

. brain-large enough to receive and process coming information and provide appropriate stimuli to the body musculature b. jaws-for acquiring, retaining and macerating food( in fishes, gills for respiration

*As braincases become larger, it became increasingly movable independent of the trunk that time. CEPHALIZATION- developed a greater degree in craniates than any other vertebrates

a. contains a cavity, the coelom, which houses most of the viscera b. surrounding the coelom is the body wall consisting of muscle, vertebral column and ribs; in many but not all,craniates paired pectoral and pelvic appendages are associated with the trunk c.neck- is a narrow extension of trunk of amphibians,reptiles and mammals and lacks a coelom; It consists of vertebrae, muscles, spinal cord, nerves and elongated tubes(esophagus,blood vessels, lymphatic, trachea) that connect the head with those of trunk.

C. TAIL-commences at the anus or vent; thus, it is postanal
-consist of: caudal continuation of body wall muscles
axial skeleton
nerves and blood vessels

-some adult craniates lack a postanal tail although it is present in all embryos -swimming larvae of frogs,toads and wormlike amphibians (caecilians) have a tail, but it is resorbed at metamorphosis -modern birds have tails reduced to a nubbin but the first birds had long tails -human beings have a vestigial post anal tail early in embryonic life. Remnant remain in adults as the tailbone(coccyx)

*Two appendages --- pectoral and pelvic
Support: internal skeleton
Operated: contributions from the trunk musculature
-mostly characteristic of vertebrates but the they are sometimes vestigial or completely gone...
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